The Preliminary Study On The Rocking Chair Archwire With Mini-implant Anchorage For Unlocking The Bite Of Adult Angle Class Ⅱ Division2Malocclusion

Objective:To investigate the clinical effects of miniscrews in the treatment of deep overbite and steep axial inclination of the upper incisors in adult Class Ⅱ division2malocclusions. Estimate the changes of the maxillary incisors and the maxillary fist molars in3dimensions, lip-mouth relationship and the occlusal contacts during opening/closing, protrusive and lateral movement of the mandibular. And then, comparing the effect between miniscrews and conventional rocking chair archwire to evaluate the difference and provide information for the clinical treatment of adult Class Ⅱ division2malocclusion.Methods:18adult patients with Class Ⅱ division2malocclusion were chosen and divided into two groups randomly:miniscrew group and conventional rocking chair archwire group. After the alignment of the upper dental arch, both groups used rocking chair archwire to level the upper curvilinear. At the same time, miniscrews were inserted into the labial alveolar bone between the roots of maxillary lateral incisors and canines in the miniserew group, and then50g force in each side was imposed by niekel titanium closed-coil springs. The cephalometric films were taken and T-Scan Ⅲ system was used to record and analyze the occlusal contacts during opening/closing, protrusive and right/left lateral movement of the mandible before the treatment and after the treatment of the deep overbite and steep axial inclination of the upper incisors. SPSS17.0was used for the statistics analysis.Results:1.In the miniscrew group, significant reductions in overbite(P<0.01), U1-PP(P<0.05) and U1-Stm(P<0.05), significant increase of overjet(P<0.01) and U1-SN (P<0.05) were observed after the treatment of steep axial inclination of the upper incisors. In the rocking chair archwire group, similar changes presented. There were significant reductions in U1-PP (P<0.05),Ul-Stm (P<0.05) and less increase in U1-SN (P<0.05) in the miniscrew group than in the rocking chair archwire group.2.In both groups, during opening/closing movement of the mandible, significant reductions in the number of occlusion contacts (P<0.05) and premature contact were observed, protrusive interference (P<0.01) increased and lateral interference (P<0.05) reduced after the treatment of steep axial inclination of the upper incisors. Compare the two groups, the miniscrew group showed less increase in protrusive interference, there was significant difference (P<0.05) in two groups.Conclusion:1.Using mini-implant anchorage to correct the deep overbite and steep axial inclination of the upper incisors of adult class Ⅱ division2malocclusion can improve the lip-teeth relationship and occlusion effectively and efficiency.2.The opening/closing and right/left lateral movement of the mandible can be more balanced but the protrusive movement get more interference especially using only rocking chair archwire after correcting of the steep axial inclination of the upper incisors of adult class II division2malocclusion.